This invention relates to a method and an apparatus for pilotless self-centering installation of a starter-alternator, and more particularly, to a method and an apparatus for pilotless self-centering installation of a starter-alternator within a vehicle which automatically and precisely aligns the starter-alternator, and which provides independent and additional support to the starter-alternator and to the vehicle""s crankshaft.
Starter-alternators are electric machines which function as both motors and generators, and are employed within vehicles to provide electrical power and torque. Particularly, starter-alternators are typically used within hybrid-electric type vehicles, and provide a variety of functions and benefits, including but not limited to generating and providing electrical power to vehicle systems and components; starting the vehicle""s engine; providing additional torque to the vehicle""s engine during heavy accelerations; assisting in and/or performing the braking functions of the vehicle, thereby capturing the kinetic energy of the moving vehicle; and stopping or xe2x80x9cshutting offxe2x80x9d the vehicle""s engine during idling and decelerating states or conditions, thereby improving the vehicle""s overall fuel economy.
Starter-alternators typically reside in the space normally occupied by a flywheel and a clutch, in the case of manual transmission type vehicles, or by a torque converter, in the case of automatic transmission type vehicles. Starter-alternators generally include a stator, which is fixedly coupled to the engine block, and a rotor, which is coupled to the crankshaft, and which is rotatably disposed within and/or is concentric to the stator. Particularly, the rotor is concentrically disposed with respect to the stator, and is separated from the stator by a relatively uniform, precise and minute gap or space, across which magnetic flux is generated.
One drawback associated with this type of starter-alternator is that the relatively uniform, precise and minute gap between the stator and the rotor is relatively difficult to create and/or form during the installation and/or assembly of the starter-alternator. Another drawback associated with this type of starter-alternator is that the rotating rotor undesirably creates and/or generates radial forces and/or loads which are transferred to the vehicle""s crankshaft. Particularly, the xe2x80x9coverhungxe2x80x9d mass of the rotor assembly is subject to and experiences what is known as the xe2x80x9cflywheel whirl effectxe2x80x9d, which causes the rotor assembly to xe2x80x9ctiltxe2x80x9d and/or move xe2x80x9coff centerxe2x80x9d as it rotates. The xe2x80x9ctiltxe2x80x9d and/or movement of the rotor assembly creates a local and/or non-uniform reduction in the relatively small and uniform gap between the stator and the rotor, thereby causing a reduction in the efficiency of the starter-alternator and a possibility of destructive contact occurring between the stator and the rotor. Furthermore, this xe2x80x9ctiltxe2x80x9d and/or movement undesirably generates a relatively high radial load or stress on the crankshaft, which can result in premature fatigue, fracture, and/or failure of the crankshaft.
Attempts have been made to maintain the precision and uniformity of the relatively small gap between the stator and the rotor, and to provide support to the rotor and the crankshaft. For example and without limitation, attempts have been made to align and/or center the rotor and the stator manually and/or by using manually operated devices or tools during the assembly and/or installation of the starter-alternator. However, these types of manual alignment procedures and tools are undesirably time-consuming and tedious to perform and/or employ. Additionally, such manual alignment procedures do not significantly reduce the stress which is transferred to the crankshaft by the substantially unsupported rotor. Other attempts have been made to tighten the specifications and/or tolerances of the components of the starter-alternator and/or of the crankshaft, and to machine and/or introduce precise pilots or piloting portions onto the components of the starter-alternator or onto the crankshaft. These prior attempts have undesirably and significantly increased the overall cost of the machining the crankshaft and/or the starter-alternator, and have not substantially reduced the stress imparted on the crankshaft.
There is therefore a need for a new and improved method and apparatus for installing a starter-alternator within a vehicle which overcomes many, if not all, of the previously delineated drawbacks of such prior methods and devices.
It is a first object of the invention to provide a method and an apparatus for installing a starter-alternator within a vehicle which overcomes at least some of the previously delineated drawbacks of prior devices, apparatuses, and methodologies.
It is a second object of the invention to provide a method and an apparatus for installing a starter-alternator within a vehicle which independently supports the rotor, thereby substantially reducing the stress transferred to the vehicle""s crankshaft.
It is a third object of the invention to provide a method and an apparatus for installing a starter-alternator within a vehicle, which substantially eliminates the need for tedious manual alignment procedures and/or tools.
According to a first aspect of the present invention, an apparatus for supporting an electric machine within a vehicle is provided. The vehicle is of the type having an engine block and a crankshaft having a rear end which extends from the engine block. The electric machine includes a stator assembly and a rotor assembly. The rotor assembly is coupled to the rear end of the crankshaft, and which is separated from the stator assembly by a relatively precise and uniform gap. The apparatus includes a generally support member which is fixedly coupled to the engine block, the support member includes a first outer lip portion upon which the stator assembly is fixedly secured and an inner lip portion. A first bearing assembly is coupled to the inner lip portion and abuttingly engages the rear end of the crankshaft, thereby radially and rotatably supporting the crankshaft. A second bearing assembly is coupled to the inner lip portion and abuttingly engages the rotor assembly, thereby radially and rotatably supporting the rotor assembly and forming the relatively precise and uniform gap.
According to a second aspect of the present invention, a method of installing a electric machine within an apparatus is provided. The apparatus is of the type having an engine block and a crankshaft having an end which extends from the engine block. The electric machine include a stator assembly and a rotor assembly, the rotor assembly is adapted to be concentrically disposed within the stator assembly, and includes a first portion which is adapted to be coupled to the first end of the crankshaft. The method comprises the steps of:
providing a support member having an inner channel; coupling the stator assembly to the support member; providing a first and a second bearing assembly;
coupling the first and second bearing assemblies to the support member and within the channel; axially aligning the channel of the support member with the end of the crankshaft; moving the support member from a first position in which the support member is remote from the engine block and a second position in which the support member abuts the engine block, the movement being effective to cause the first bearing engage the end of the crankshaft, thereby automatically centering the first member and the stator assembly with respect to the crankshaft; axially aligning the rotor assembly with the end of the crankshaft; and moving the rotor assembly from a first position in which the support member is remote from the end portion of the crankshaft and a second position in which the support member abuts the end portion of the crankshaft, the movement being effective to cause the second bearing to engage the rotor assembly, thereby automatically centering the rotor assembly within the stator assembly.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.